This invention relates to novel cysteine cathepsin inhibitors and their pharmaceutical use for the treatment or prophylaxis of diseases or medical conditions in which cathepsins are implicated.
The cysteine cathepsins, e.g. cathepsins B, L and S, are a class of lysosomal enzymes which are implicated in various disorders including inflammation, rheumatoid arthritis, osteoarthritis, osteoporosis, tumors (especially tumor invasion and tumor metastasis), coronary disease, atherosclerosis (including atherosclerotic plaque rupture and destabilization), autoimmune diseases, respiratory diseases (including asthma and chronic obstructive pulmonary disease), infectious diseases and immunologically mediated diseases (including transplant rejection).
The compounds of the invention are particularly useful as cathepsin inhibitors, primarily as cathepsin B inhibitors, and can be used for the treatment of the above-cited cathepsin dependent conditions.
The invention relates to the novel cathepsin inhibitors of the formula 
wherein
R1 is aryl or biaryl;
R2 is aryl-lower alkyl, biaryl-lower alkyl, benzo-fused cycloalkyl, cycloalkyl-lower alkyl, bicycloalkyl-lower alkyl, aryloxy-lower alkyl, or aryl-C2-C7-alkyl in which C2-C7-alkyl is interrupted by Y;
Y is O, S, SO, SO2, CO or NR6;
R3 is hydrogen or lower alkyl; or
R2 and R3 combined are C2-C7-alkylene or C2-C7-alkylene interrupted by Y;
R4 is hydrogen or lower alkyl;
R5 is hydrogen, optionally substituted lower alkyl, aryl-lower alkyl, biaryl-lower alkyl, cycloalkyl-lower alkyl, bicycloalkyl-lower alkyl, aryloxy-lower alkyl, or aryl-C2-C7-alkyl in which C2-C7-alkyl is interrupted by Y;
R6 is hydrogen, lower alkyl or aryl-lower alkyl;
and pharmaceutically acceptable salts thereof.
A particular embodiment of the invention relates to the compounds of formula I wherein R5 represents the grouping
xe2x80x94Xxe2x80x94Arxe2x80x94Qxe2x80x94Z
in which X is lower alkylene, lower alkyleneoxy or C2-C7-alkylene interrupted by Y; Ar is monocyclic carbocyclic or monocyclic heterocyclic arylene; Q is a direct bond, lower alkylene, or thio- or oxy-lower alkylene: Z is hydroxy, acyloxy, carboxyl, or carboxyl derivatized as a pharmaceutically acceptable ester or amide; or Z is 5-tetrazolyl; Y is O, S, SO, SO2 or NR6; and R6 is hydrogen, lower alkyl or aryl-lower alkyl; and pharmaceutically acceptable salts thereof.
A specific embodiment of the invention relates to the compounds of formula II 
wherein
R1 is aryl or biaryl;
Rxe2x80x22 aryl-lower alkyl, biaryl-lower alkyl, benzo-fused cycloalkyl, cycloalkyl-lower alkyl or bicycloalkyl-lower alkyl;
Ar is monocyclic carbocyclic or monocyclic heterocyclic arylene;
Xxe2x80x2 is lower alkylene or C2-C7-alkylene interrupted by Yxe2x80x2;
Yxe2x80x2 is O or S;
Q is a direct bond, lower alkylene, or thio- or oxy-lower alkylene; and
Zxe2x80x2 is carboxyl, carboxyl derivatized as a pharmaceutically acceptable ester or amide, 5-tetrazolyl, or hydroxymethyl;
and pharmaceutically acceptable salts thereof.
A specific embodiment of the invention is directed to compounds of formula II wherein R1 is aryl; Rxe2x80x22 is aryl-lower alkyl, Xxe2x80x2 is C1-C5-alkylene, or Xxe2x80x2 is C2-C4-alkylene interrupted by O or S; Ar is monocyclic carbocyclic arylene; Q is a direct bond, oxy-C1-C4-alkylene or C1-C4-alkylene; and Zxe2x80x2 is carboxyl or carboxyl derivatized as a pharmaceutically acceptable ester; and pharmaceutically acceptable salts thereof.
A more specific embodiment of the invention is directed to compounds of formula If wherein R1 is monocyclic carbocyclic aryl; Rxe2x80x22 is carbocyclic aryl-methyl; Xxe2x80x2 is C1-C3-alkylene; or Xxe2x80x2 is C2-alkylene interrupted by O; Ar is monocarbocyclic arylene; Q is a direct bond or oxymethylene; Zxe2x80x2 is carboxyl, carboxyl derivatized as a pharmaceutically acceptable ester, or 5-tetrazolyl; and pharmaceutically acceptable salts thereof.
A particular embodiment of the invention relates to the compounds of the formula IIa 
wherein Rxe2x80x22, Xxe2x80x2, Ar, Q and Zxe2x80x2 have meaning as defined above, W represents O, CH2 or NR6 in which R6 is lower alkyl; and R7 and R8 independently represent hydrogen or lower alkyl; or R7 and R8 together represent oxo; and pharmaceutically acceptable salts thereof.
Another embodiment of the invention relates to compounds of formula III 
wherein
R1 is aryl or biaryl;
Rxe2x80x32 is aryl-lower alkyl, biaryl-lower alkyl, cycloalkyl-lower alkyl or bicycloalkyl-lower alkyl;
Ar is monocyclic carbocyclic or monocyclic heterocyclic arylene;
Xxe2x80x3 is lower alkylene;
Qxe2x80x2 is a direct bond or lower alkylene;
Zxe2x80x3 is carboxyl, carboxyl derivatized as a pharmaceutically acceptable ester, or 5-tetrazolyl;
and pharmaceutically acceptable salts thereof.
A specific embodiment of the invention relates to compounds of formula III wherein R1 is monocyclic carbocyclic or heterocyclic aryl; Rxe2x80x32 is aryl-lower alkyl; Qxe2x80x2 is a direct bond or lower alkylene; and Zxe2x80x3 is carboxyl; and pharmaceutically acceptable salts thereof.
A more specific embodiment relates to the compounds of formula III wherein R1 is monocyclic carbocyclic aryl; Rxe2x80x32 is carbocyclic aryl-methyl; Xxe2x80x3 is C3-alkylene; Ar is monocyclic carbocyclic arylene; Qxe2x80x2 is a direct bond; Zxe2x80x3 is carboxyl; and pharmaceutically acceptable salts thereof.
The compounds of the invention depending on the nature of substituents, possess one or more asymmetric carbons. The resulting diastereomers and enantiomers are encompassed by the instant invention.
Preferred are the compounds of the invention wherein the asymmetric carbon to which are attached R2 and/or R3 corresponds to that of an L-amino acid precursor and the asymmetric carbon to which is attached the cyano group also corresponds to that of an L-amino acid; both asymmetric centers are typically assigned the (S)-configuration. As an illustration, the preferred compounds of the formula I wherein R3 and R4 represent hydrogen can be represented by formula IV 
wherein R1, R2 and R5 have meaning as previously defined.
Particularly preferred are the compounds of the formula V 
wherein Rxe2x80x21 and Ra are aryl; W is O or CH2; Arxe2x80x2 is arylene selected from pyridylene, furanylene, thienylene, thiazolylene, phenylene or phenylene substituted by 1 to 3 of alkyl or halo; pharmaceutically acceptable salts thereof; and pharmaceutically acceptable esters thereof.
Further preferred are the compounds of formula V wherein Rxe2x80x21 and Ra are independently phthalidyl, phenyl, or phenyl mono-, di- or tri-substituted by lower alkyl, halo, trifluoromethyl, cyano, nitro, hydroxy, acyloxy, acyl, carboxyl, lower alkylsulfonyl, or esterified or amidated carboxyl; W is O; Arxe2x80x2 is 1,3-phenylene or 1,3-phenylene mono- or di-substituted by chloro or fluoro; pharmaceutically acceptable salts thereof; and pharmaceutically acceptable esters thereof.
Especially preferred are the compounds of formula V wherein Rxe2x80x21 is phthalidyl, phenyl, or phenyl mono- or disubstituted by halo, lower alkyl or esterified or amidated carboxyl; Ra is 3-tolyl; W is O; Arxe2x80x2 is 1,3-phenylene or 1,3-phenylene mono- or disubstituted by chloro or fluoro; pharmaceutically acceptable salts thereof; and pharmaceutically acceptable esters thereof.
Further preferred are the compounds of formula V wherein Rxe2x80x21 is phenyl; Ra is 3-tolyl; W is O; Arxe2x80x2 is 1,3-phenylene or 1,3-phenylene mono- or disubstituted by chloro or fluoro; pharmaceutically acceptable salts thereof; and pharmaceutically acceptable esters thereof.
The general definitions used herein have the following meaning within the scope of the invention, unless otherwise specified.
The term xe2x80x9clowerxe2x80x9d referred to above and hereinafter in connection with organic radicals or compounds respectively defines such as branched or unbranched with up to and including 7, preferably up to and including 4 and advantageously one or two carbon atoms.
Alkyl represents C1-C20-alkyl, preferably lower alkyl, which may be substituted as described below.
Optionally substituted lower alkyl refers to unsubstituted or substituted straight or branched chain hydrocarbon groups having 1 to 7 carbon atoms, preferably 1 to 4 carbon atoms. Substituted lower alkyl groups include, but are not limited to, alkyl groups substituted by one or more of the following groups: halo, hydroxy, acyloxy, alkoxy, amino, alkylamino, dialkylamino, acylamino, mercapto, alkylthio, alkylsulfinyl, alkylsulfonyl, arylsulfonyl (including heteroarylsulfonyl), aminosulfonyl, nitro, cyano, carboxyl, alkoxycarbonyl, pyrrolidyl, piperidyl, morpholinyl, (alkyloxy, carboxy, alkoxycarbonyl)-alkoxy, and the like.
A lower alkyl group is branched or unbranched and contains 1 to 7 carbon atoms, preferably 1-4 carbon atoms. Lower alkyl represents for example methyl, ethyl, propyl, butyl, isopropyl or isobutyl.
Lower alkylene represents either straight chain or branched alkylene of 1 to 7 carbon atoms and represents preferably straight chain alkylene of 1 to 4 carbon atoms, e.g. a methylene, ethylene, propylene or butylene chain, or said methylene, ethylene, propylene or butylene chain mono-substituted by C1-C3-alkyl (advantageously methyl) or disubstituted on the same or different carbon atoms by C1-C3-alkyl (advantageously methyl), the total number of carbon atoms being up to and including 7.
A lower alkoxy (or alkyloxy) group preferably contains 1-4 carbon atoms, advantageously 1-3 carbon atoms, and represents for example ethoxy, propoxy, isopropoxy, or most advantageously methoxy.
Halogen (halo) preferably represents chloro or fluoro but may also be bromo or iodo.
Aryl represents carbocyclic or heterocyclic aryl.
Carbocyclic aryl represents monocyclic or bicyclic aryl, for example phenyl or phenyl mono-, di- or tri-substituted by one, two or three radicals selected from optionally substituted lower alkyl, lower alkoxy, hydroxy, amino, halogen, cyano and trifluoromethyl, or substituted by C3-C5-alkylene, lower alkylenedioxy or oxy-C2-C3-alkylene on adjacent carbon atoms; or 1- or 2-naphthyl. Lower alkylenedioxy is a divalent substituent attached to two adjacent carbon atoms of phenyl, e.g. methylenedioxy or ethylenedioxy. Oxy-C2-C3-alkylene is also a divalent substituent attached to two adjacent carbon atoms of phenyl, e.g. oxyethylene or oxypropylene. An example for oxy-C2-C3-alkylene substituted phenyl is 2,3-dihydrobenzofuran-5-yl. Alkylene substituted phenyl is e.g. indanyl or tetralinyl.
Preferred as carbocyclic aryl is phenyl or phenyl mono- or disubstituted by lower alkoxy, halogen, lower alkyl or trifluoromethyl, especially phenyl or phenyl monosubstituted by lower alkoxy, halogen or trifluoromethyl, and in particular phenyl.
Heterocyclic aryl represents monocyclic or bicyclic heteroaryl, for example pyridyl, indolyl, isoindolyl, quinoxalinyl, quinolinyl, isoquinolinyl, benzothienyl, benzofuranyl, benzopyranyl, benzothiopyranyl, furanyl, pyrrolyl, thiazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl, thienyl, or any said radical substituted, especially mono- or di-substituted, by e.g. lower alkyl, lower alkoxy or halogen. Pyridyl represents 2-, 3- or 4-pyridyl. Thienyl represents 2- or 3-thienyl. Quinolinyl represents preferably 2-, 3- or 4-quinolinyl. Isoquinolinyl represents preferably 1-, 3- or 4-isoquinolinyl. Benzopyranyl, benzothiopyranyl represent preferably 3-benzopyranyl or 3-benzothiopyranyl, respectively. Thiazolyl represents preferably 2- or 4-thiazolyl. Triazolyl is preferably 1-, 2- or 5-(1,2,4-triazolyl). Tetrazolyl is preferably 5-tetrazolyl.
Preferably, heterocyclic aryl is pyridyl, indolyl, quinolinyl, pyrrolyl, thiazolyl, isoxazolyl, triazolyl, tetrazolyl, pyrazolyl, imidazolyl, thienyl, or any said radical substituted, especially mono- or di-substituted, by lower alkyl or halogen; and in particular pyridyl.
Aryl, for example in conjunction with R1, also represents a grouping of the general formula 
wherein W is O, CH2 or NR6; R6, R7 and R8 represent independently hydrogen or lower alkyl; or R7 and R8 combined represent oxo; and the line represents the point of attachment. Illustrative thereof is 3-oxo-1,3-dihydrobenzofuran-5-yl (5-phthalidyl).
Aryl, for example in conjunction with R5, also represents a heterocyclic or carbocyclic aromatic ring system as defined above which is substituted by the grouping xe2x80x94Qxe2x80x94Z in which Q is a direct bond, lower alkylene, or thio- or oxy-lower alkylene; and Z is hydroxy, acyloxy, carboxyl or carboxyl derivatized as a pharmaceutically acceptable ester or amide; or Z is 5-tetrazolyl.
Arylene (Ar in formula II) is an aryl linking group in which aryl is monocyclic heterocyclic or carbocyclic aryl.
A heterocyclic aryl linking group is for instance (but not limited thereto) 1,3-pyrazolyl, 2,4- or 2,6-pyridyl, 2,5-thienyl, 2,4-thiazolyl, 2,5-furanyl or 1,4-imidazolyl in which the groups as depicted in formula II are attached to the ring at the indicated positions.
A carbocyclic aryl linking group is for instance (but not limited thereto) optionally substituted phenyl and in which the two groups as depicted in formula II are attached ortho, meta or para to each other, preferably meta. Optional substituents are e.g. halo, alkyl and the like.
Biaryl is preferably carbocyclic biaryl, e.g. biphenyl, namely 2-, 3- or 4-biphenyl, advantageously 4-biphenyl, each optionally substituted by e.g. lower alkyl, lower alkoxy, halogen, trifluoromethyl or cyano.
Cycloalkyl represents a saturated cyclic hydrocarbon optionally substituted by lower alkyl which contains 3 to 10 ring carbons and is advantageously cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl optionally substituted by lower alkyl.
Benzo-fused cycloalkyl represents for example indanyl, tetralinyl and the like.
Bicycloalkyl is for example norbornanyl.
Aryl-lower alkyl represents (carbocyclic aryl or heterocylic aryl)-lower alkyl.
Carbocyclic aryl-lower alkyl represents preferably straight chain or branched aryl-C1-4-alkyl in which carbocyclic aryl has meaning as defined above, e.g. benzyl or phenyl-(ethyl, propyl or butyl), each unsubstituted or substituted on phenyl ring as defined under carbocyclic aryl above, advantageously optionally substituted benzyl, e.g. benzyl substituted by lower alkyl, lower alkoxy and the like.
Heterocyclic aryl-lower alkyl represents preferably straight chain or branched heterocyclic aryl-C1-4-alkyl in which heterocyclic aryl has meaning as defined above, e.g. 2-, 3- or 4-pyridylmethyl or (2,3- or 4-pyridyl)-(ethyl, propyl or butyl); or 2- or 3-thienylmethyl or (2- or 3-thienyl)-(ethyl, propyl or butyl); 2-, 3- or 4-quinolinylmethyl or (2-, 3- or 4-quinolinyl)-(ethyl, propyl or butyl); or 2- or 4-thiazolylmethyl or (2- or 4-thiazolyl)-(ethyl, propyl or butyl); 3-indolylmethyl or 3-indolyl-(ethyl, propyl or butyl); 2- or 3-furanylmethyl; and said heterocyclic aryl group being optionally substituted by e.g. lower alkyl or lower alkoxy.
Cycloalkyl-lower alkyl represents e.g. (cyclopentyl- or cyclohexyl)-(methyl or ethyl).
Biaryl-lower alkyl represents e.g. 4-biphenylyl-(methyl or ethyl).
Acyl as in acyloxy is derived from an organic carboxylic acid, carbonic acid or carbamic acid. Acyl represents e.g. lower alkanoyl, carbocyclic aryl-lower alkanoyl, lower alkoxycarbonyl, aroyl, di-lower alkylaminocarbonyl or di-lower alkylamino-lower alkanoyl. Preferably, acyl is lower alkanoyl.
Lower alkanoyl represents e.g. C1-7-alkanoyl including formyl, and is preferably C2-4-alkanoyl such as acetyl or propionyl.
Aroyl represents e.g. benzoyl or benzoyl mono- or di-substituted by one or two radicals selected from lower alkyl, lower alkoxy, halogen, cyano and trifluoromethyl; or 1- or 2-naphthoyl; and also e.g. pyridylcarbonyl.
Lower alkoxycarbonyl represents preferably C1-4-alkoxycarbonyl, e.g. ethoxycarbonyl.
Carboxyl derivatized as a pharmaceutically acceptable ester is for example an optionally substituted lower alkyl ester, such as lower alkoxycarbonyl.
Carboxyl derivatized as a pharmaceutically acceptable amide is for example aminocarbonyl, mono- or di-lower alkylaminocarbonyl.
Pharmaceutically acceptable salts of the acidic compounds of the invention are salts formed with bases, namely cationic salts such as alkali and alkaline earth metal salts, such as sodium, lithium, potassium, calcium, magnesium, as well as ammonium salts, such as ammonium, trimethyl-ammonium, diethylammonium, and tris-(hydroxymethyl)-methyl-ammonium salts.
Similarly acid addition salts, such as of mineral acids, organic carboxylic and organic sulfonic acids e.g. hydrochloric acid, methanesulfonic acid, maleic acid, are also possible provided a basic group, such as pyridyl, constitutes part of the structure.
The compounds of the invention exhibit valuable pharmacological properties in mammals including man and are particularly useful as cysteine cathepsin inhibitors.
As the compounds of the invention are inhibitors of cysteine cathepsin enzymes, they are particularly useful in mammals as agents for the treatment of e.g. osteoarthritis, rheumatoid arthritis, tumor metastasis, and atherosclerotic plaque rupture and plaque destabilization.
Beneficial effects are evaluated in in vitro and in vivo pharmacological tests generally known in the art, and as illustrated herein.
The above cited properties are demonstrable in in vitro and in vivo tests, using advantageously mammals, e.g. rats, mice, dogs, or isolated organs and tissues, as well as mammalian enzyme preparations, either natural or prepared by e.g. recombinant technology. Said compounds can be applied in vitro in the form of solutions, e.g. preferably aqueous solutions or suspensions, and in vivo either enterally or parenterally, advantageously orally, e.g. as a suspension or in aqueous solution, or as a solid capsule formulation. The dosage in vitro may range between about 10xe2x88x925 molar and 10xe2x88x929 molar concentrations. The dosage in vivo may range, depending on the route of administration, between about 0.1 and 100 mg/kg.
The cathepsin inhibitory effects of the compound of the invention can be determined in vitro by measuring the inhibition of e.g. recombinant human cathepsins B, L and S. The buffer used in the assays is a 0.1 M pH 5.8 phosphate buffer containing EDTA (1.33 mM), DTT (2.7 mM) and Brij (0.03%).
The in vitro assays are carried out as follows:
(a) For Cathepsin B:
To a microtiter well is added 100 uL of a 20 uM solution of inhibitor in assay buffer followed by 50 uL of a 6.4 mM solution of Zxe2x80x94Argxe2x80x94Argxe2x80x94AMC substrate (Peptides International) in assay buffer. After mixing, 50 uL of a 0.544 nM solution of recombinant human cathepsin B in assay buffer is added to the well, yielding a final inhibitor concentration of 10 uM. Enzyme activity is determined by measuring fluorescence of the liberated aminomethylcoumarin at 440 nM using 380 nM excitation, at 20 minutes. % Enzyme inhibition is determined by comparison of this activity to that of a solution containing no inhibitor. Compounds are subsequently subjected to a dose response curve analysis to determine IC50 values.
(b) For Cathepsin L:
Recombinant human cathepsin L is activated prior to use in this assay: To 500 uL of a 510 nM solution of cathepsin L in a 50 mM pH 5.0 acetate buffer containing 1 mM EDTA, 3 mM DTT and 150 mM NaCl is added 10 uL of a 625 uM solution of dextran sulfate (ave. mw=8000), and the resulting solution is incubated on ice for 30 min. 4 uL of this solution is then diluted into 46 uL assay buffer, yielding a 40 nM enzyme solution.
To perform the assay, 100 uL of a 20 uM solution of inhibitor in assay buffer is added to a microtiter well. 50 uL of a 20 uM solution of Z-Phe-Arg-AMC (Peptides International) is then added. After mixing, 50 uL of the activated 40 nM solution of recombinant human cathepsin L in assay buffer is then added to the well, yielding a final inhibitor concentration of 10 uM. Enzyme activity is determined by measuring fluorescence of the liberated aminomethylcoumarin at 440 nM using 380 nM excitation of 20 minutes. % Enzyme inhibition is determined by comparison of this activity to that of a solution containing no inhibitor. Compounds are subsequently subjected to a dose response curve analysis to determine IC50 values.
(c) For Cathepsin S:
To a microtiter well is added 100 uL of a 20 uM solution of inhibitor is assay buffer. 50 uL of a 700 uM solution of Z-Val-Val-Arg-AMC substrate (Peptides International) is then added. After mixing, 50 uL of a 5.2 nM solution of recombinant human cathepsin S in assay buffer is then added to the well, yielding a final inhibitor concentration of 10 uM. Enzyme activity is determined by measuring fluorescence of the liberated aminomethylcoumarin at 440 nM using 380 nM excitation at 200 minutes. % Enzyme inhibition is determined by comparison of this activity to that of a solution containing no inhibitor. Compounds are subsequently subjected to a dose response curve analysis to determine IC50 values.
Compounds of the invention, primarily those in which R5 represents the grouping xe2x80x94Xxe2x80x94Arxe2x80x94Qxe2x80x94Z, are typically selective cathepsin B inhibitors. IC50 values may range between about 10 and 1000 nM, preferably between about 10 and 200 nM.
Illustrative of the invention, the IC50 in the in vitro cathepsin B assay is about 100 nM for the compound of example 6.
The antiarthritic efficacy of the compounds of the invention for the treatment of rheumatoid arthritis can be determined using the rat model of adjuvant arthritis, as described previously (R. E. Esser, et. al. J. Rheumatology, 1993, 20, 1176.)
The efficacy of the compounds of the invention for the treatment of osteoarthritis can be determined using the rabbit partial lateral meniscectomy model, as described previously (Colombo et al. Arth. Rheum. 1993 26, 875-886). The efficacy of the compounds in the model can be quantified using histological scoring methods, as described previously (O""Byrne et al. Inflamm Res 1995, 44, S117-S118).
The compounds of the invention are prepared by:
(a) condensing a compound of the formula VI 
wherein R4 and R5 have meaning as defined herein, with an acid of formula VII 
wherein R1, R2 and R3 have meaning as defined above; or with a reactive derivative thereof; or
(b) condensing a compound of the formula VIII 
wherein R2, R3, R4, and R5 have meaning as defined herein, with a reactive aryl reagent corresponding to the aryl group R1; and in above processes, if required, temporarily protecting any interfering reactive groups and then isolating the resulting compound of the invention; and, if desired, converting any resulting compound into another compound of the invention; and/or if desired, converting a resulting compound into a salt or a resulting salt into the free acid or base or into another salt.
In starting compounds and intermediates, which are converted to the compounds of the invention in a manner described herein, functional groups present such as amino, hydroxy and carboxyl groups, are optionally protected by conventional protecting groups that are common in preparative organic chemistry. Protected hydroxy, amino and carboxyl groups are those that can be converted under mild conditions into free amino, hydroxy and carboxyl groups without other undesirable side reactions taking place. For example, carboxyl protecting groups are allyl, benzyl or substituted benzyl groups, and the like.
The preparation of any nitrile intermediates from the corresponding primary amides, can be carried out according to methods well known in the art for the dehydration of a primary amide to a nitrile, e.g. with thionyl chloride or oxalyl chloride in the presence of a base. A preferred procedure involves the treatment with oxalyl chloride and pyridine in DMF at or below room temperature.
The starting materials of formula VIII can be prepared by condensing a nitrile of formula VI with a protected amino acid of formula IX 
wherein R2 and R3 have meaning as defined herein and Rp is an amino protecting group, preferably 1-butoxycarbonyl.
The condensation can be carried out according to methods well-known in the art, e.g. by reacting a nitrile of formula VI with a protected amino acid of formula IX in the presence of a condensing agent such as N-(3-dimethylaminopropyl)-Nxe2x80x2-ethylcarbodiimide, optionally in the presence of e.g. hydroxybenzotriazole or 1-hydroxy-7-azabenzotriazole, and a base such as N-methylmorpholine, followed by deprotection (e.g. with formic acid) of the t-butoxycarbonyl (Boc) group.
The protected amino acids of formula IX and aminonitriles of formula VI are either known or can be prepared according to methodology known in the art and illustrated herein.
N-Arylaminoacids of formula VII can be prepared through reaction of the appropriate aryl iodide with an amino acid or aminoacid HCl salt, in the presence of Pd(Oac)2, CuI, TEBA, K2CO3, DMF, water, triethylamine and tri-o-tolylphosphine, as described in Tetrahedron: Asymmetry 1996, 7, 3075. Aryl iodides are either commercially available, or are prepared from the corresponding aniline, using standard procedures (NaNO2,HCl, KI).
The optically active N-arylaminoacids of formula VII can also be prepared through conversion of the ester of the opposite enantiomer of the amino acid to its corresponding xcex1-hydroxyester, followed by triflation, arylamine displacement, and ester hydrolysis as illustrated below: 
Aminonitriles of formula VI and prepared e.g. through conversion of the Boc-protected amino acid to its corresponding primary amide, followed by dehydration, using thionyl chloride, oxalyl chloride or some other dehydrating reagent, and then Boc deprotection using formic acid as illustrated below. 
For example, the compounds of formula VIa wherein R5 is xe2x80x94Xxe2x80x94Arxe2x80x94Qxe2x80x94Z, in which X is lower alkylene interrupted by 0, and Ar, Z and Q have meaning as defined above, are prepared by first reacting, e.g. a compound of the formula X 
wherein Rp is an NH protecting group, such as t-butoxycarbonyl (Boc), with e.g. a compound of the formula XI
Zxe2x80x94Qxe2x80x94Arxe2x80x94CH2xe2x80x94Vxe2x80x83xe2x80x83(XI)
wherein Ar and Q have meaning as defined above, Z being e.g. esterified carboxyl such as trimethylsilyloxyethylcarbonyl, lower alkoxycarbonyl or allyloxycarbonyl, and V is a reactive leaving group such as halo or lower alkylsulfonyloxy. The condensation is carried out in the presence of 2 equivalents of a strong base, e.g. sodium hydride in an anhydrous solvent such as dimethylformamide, to obtain an acid of formula XII 
wherein Rp, Ar, Q and Z have meaning as defined herein. Such is converted to the corresponding compound of formula VI as described above.
The starting amino acids (wherein R1 is hydrogen in formula VII) are either known in the art or are prepared according to methods known in the art.
The condensation according to process (b) is carried out by e.g. coupling the amine of formula VIIIa with tri-arylbismuth diacetate (Chem. Rev. 1989, 89, 1487) or arylboronic acid (Tetrahedron Let., 1998, 39, 2933) catalyzed by cupric acetate, as illustrated below for the preparation of a compound of formula IV. 
In the above processes, when R5 has a protected carboxylic acid substituent, this group is deprotected in the final step, e.g. using Pd(0) and morpholine if the acid is protected as its allyl ester, or using LiI/pinacolone if the acid is protected as its methyl ester, or using tetrabutyl amonium fluoride in THF, if the protecting group is a trimethylsilylethyl ester. When R5 contains a protected tetrazole substituent, e.g. the cyanoethyl protecting group is removed in the final step using DBU in CH2Cl2, as illustrated in the examples.
Finally, compounds of the invention are either obtained in the free form, or as a salt thereof if salt forming groups are present.
Any acidic compounds of the invention may be converted into metal salts with pharmaceutically acceptable bases, e.g. an aqueous alkali metal hydroxide, advantageously in the presence of an ethereal or alcoholic solvent, such as a lower alkanol. Resulting salts may be converted into the free compounds by treatment with acids. These or other salts can also be used for purification of the compounds obtained. Ammonium salts are obtained by reaction with the appropriate amine, e.g. diethylamine, and the like.
Compounds of the invention having basic groups can be converted into acid addition salts, especially pharmaceutically acceptable salts. These are formed, for example, with inorganic acids, such as mineral acids, for example sulfuric acid, a phosphoric or hydrohalic acid, or with organic carboxylic acids, such as (C1-C4)alkanecarboxylic acids which, for example, are unsubstituted or substituted by halogen, for example acetic acid, such as saturated or unsaturated dicarboxylic acids, for example oxalic, succinic, maleic or fumaric acid, such as hydroxycarboxylic acids, for example glycolic, lactic, malic, tartaric or citric acid, such as amino acids, for example aspartic or glutamic acid, or with organic sulfonic acids, such as (C1-C4)-alkylsulfonic acids (for example methanesulfonic acid) or arylsulfonic acids which are unsubstituted or substituted (for example by halogen). Preferred are salts formed with hydrochloric acid, methanesulfonic acid and maleic acid.
In view of the close relationship between the free compounds and the compounds in the form of their salts, whenever a compound is referred to in this context, a corresponding salt is also intended, provided such is possible or appropriate under the circumstances.
The compounds, including their salts, can also be obtained in the form of their hydrates, or include other solvents used for their crystallization.
The pharmaceutical compositions according to the invention are those suitable for enteral, such as oral or rectal, transdermal, topical, and parenteral administration to mammals, including man, to inhibit cathepsin activity, and for the treatment of cathepsin dependent disorders, and comprise an effective amount of a pharmacologically active compound of the invention, alone or in combination, with one or more pharmaceutically acceptable carriers.
More particularly, the pharmaceutical compositions comprise an effective cathepsin inhibiting amount of a compound of the invention.
The pharmacologically active compounds of the invention are useful in the manufacture of pharmaceutical compositions comprising an effective amount thereof in conjunction or admixture with excipients or carriers suitable for either enteral or parenteral application. Preferred are tablets and gelatin capsules comprising the active ingredient together with a) diluents, e.g. lactose, dextrose, sucrose, mannitol, sorbitol, cellulose and/or glycine; b) lubricants, e.g. silica, talcum, stearic acid, its magnesium or calcium salt and/or polyethyleneglycol; for tablets also c) binders e.g. magnesium aluminum silicate, starch paste, gelatin, tragacanth, methylcellulose, sodium carboxymethylcellulose and or polyvinylpyrrolidone; if desired d) disintegrants, e.g. starches, agar, alginic acid or its sodium salt, or effervescent mixtures; and/or e) absorbents, colorants, flavors and sweeteners. Injectable compositions are preferably aqueous isotonic solutions or suspensions, and suppositories are advantageously prepared from fatty emulsions or suspensions. Said compositions may be sterilized and/or contain adjuvants, such as preserving, stabilizing, wetting or emulsifying agents, solution promoters, salts for regulating the osmotic pressure and/or buffers. In addition, they may also contain other therapeutically valuable substances. Said compositions are prepared according to conventional mixing, granulating or coating methods, respectively, and contain about 0.1 to 75%, preferably about 1 to 50%, of the active ingredient.
Tablets may be either film coated or enteric coated according to methods known in the art.
Suitable formulations for transdermal application include an effective amount of a compound of the invention with carrier. Advantageous carriers include absorbable pharmacologically acceptable solvents to assist passage through the skin of the host. For example, transdermal devices are in the form of a bandage comprising a backing member, a reservoir containing the compound optionally with carriers, optionally a rate controlling barrier to deliver the compound of the skin of the host at a controlled and predetermined rate over a prolonged period of time, and means to secure the device to the skin.
Suitable formulations for topical application, e.g. to the skin and eyes, are preferably aqueous solutions, ointments, creams or gels well-known in the art. Such may contain solubilizers, stabilizers, tonicity enhancing agents, buffers and preservatives.
The pharmaceutical formulations contain an effective cathepsin inhibiting amount of a compound of the invention as defined above, either alone or in combination with another therapeutic agent.
In conjunction with another active ingredient, a compound of the invention may be administered either simultaneously, before or after the other active ingredient, either separately by the same or different route of administration or together in the same pharmaceutical formulation.
The dosage of active compound administered is dependent on the species of warm-blooded animal (mammal), the body weight, age and individual condition, and on the form of administration. A unit dosage for oral administration to a mammal of about 50 to 70 kg may contain between about 10 and 500 mg of the active ingredient.
The present invention also relates to methods of using the compounds of the invention and their pharmaceutically acceptable salts, or pharmaceutical compositions thereof, in mammals to inhibit cathepsins, such as cathepsin B, L and/or S, and for the treatment of cathepsin dependent conditions, such as cathepsin B, L and/or S dependent conditions, described herein, e.g. inflammation, rheumatoid arthritis and osteoarthritis.
Particularly the present invention relates to a method of selectively inhibiting cathepsin activity in a mammal which comprises administering to a mammal in need thereof an effective cathepsin inhibiting amount of a compound of the invention.
More specifically such relates to a method of treating rheumatoid arthritis, osteoarthritis, and inflammation in mammals which comprises administering to a mammal in need thereof a correspondingly effective amount of a compound of the invention.
The following examples are intended to illustrate the invention and are not to be construed as being limitations thereon. Temperatures are given in degrees Centrigrade. If not mentioned otherwise, all evaporations are performed under reduced pressure, preferably between about 15 and 100 mm Hg (=20-133 mbar). The structure of final products, intermediates and starting materials is confirmed by standard analytical methods, e.g. microanalysis and spectroscopic characteristics (e.g. MS, IR, NMR). Abbreviations used are those conventional in the art, for example:
AIBN=2,2xe2x80x2-Azobisisobutyronitrile
NBS=N-Bromosuccinimide
TEBA=Triethylbenzylammonium chloride
Boc=t-Butoxycarbonyl
DBU=1,8-Diazabicyclo[5.4.0]undec-7-ene
TPTU=O-(1,2-Dihydro-2-oxo-1-pyridyl)-N,N,Nxe2x80x2,Nxe2x80x2-tetramethyluronium tetrafluoroborate
EDCI=1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride
HOBT=1-Hydroxybenzotriazole hydrate
HOAT=1-Hydroxy-7-azabenzotriazole
NMM=N-Methylmorpholine